One of the simplest methods to encrypt a message is by using a key that defineshow many positions the letters in the text is replaced.If you encrypt a text with a key 3, all letters in the original text moves down thealphabet by 3 positions.If you decrypt a text with a key 3, all letters in the decrypted text moves up thealphabet by 3 positions (i.e d a ; f c; etc )

e.gif you encrypt the text ?trial? with a key of 3, it will become ?wuldo?if you decrypt the text ?wuldo? with a key of 3, it becomes ?trial?

(a) Write an M-file to can decrypt the following message ?brx pdqdjhg wr grlw.? using a key of 3.(b) Write an M-file that can load the text file ?encrypted_text.txt?

Notes:i. Only alpha-characters have been encrypted. Punctuations and whitespaces have not been altered and as such in your codes, you should notdecrypt any punctuations or white spaces.ii. The alphabet has 26 letters. So your encryption key should always bebetween 1 and 26.iii. You might use MATLAB inbuilt function ?find?iv. See more hints in the lab4presentation file on moodle